Screen/Linux: Remove Intel-SNA workaround - It didn't work around :-(

Doesn't have expected effect, probably due to other bugs in SNA. Causes
a complete graphics system hang instead.

So situation now (further testing pending) seems to be that the latest
2.20.16+ drivers work well if Option "TripleBuffer" "Off" is specified
in xorg.conf, and don't work in any meaningful way for us at all if the
option is omitted.

Also add some more references to help SyncTrouble - Linux section.
Screen for 32-Bit Octave on Linux rebuilt for testing.
Remaining Screen mex files for Linux rebuilt.

64-Bit Octave, 32/64-Bit Matlab rebuilt.
32-Bit Octave already in previous commit.
This is the final set of Mex files for the beta release. Everything
tested to death. Intel gpu's now work reasonable ok:

With the broken drivers (v2.20.15 and earlier), UXA works well:
Triplebuffering is detected and reported to user with info what to do.
Broken swap scheduling is detected and automatic fix applied which
fixes it perfectly reliably - although at cost of slightly lower
performance under heavy load. SNA is hopeless: Gets reported as broken,
but absolutely no way to fix it - except for a driver upgrade.

Intel drivers of v2.20.16 and later (source release at 15th December
2012) are bug-free wrt. to swap scheduling and timestamping for our
purposes. Screen handles them properly, both with UXA and SNA path.

Tested on HP Mini Atom Netbook (Dualcore Atom 1.6 Ghz, 2 GB RAM, Intel
GMA-950 / Intel 945 GME chipset, aka Gen3 hardware), tested on 32-Bit
Ubuntu 12.10 with 2.20.9 driver of distribution and with self-compiled
2.20.17+ driver from current intel master repo.

-> Mex files ready for release.
Some documentation updates...